Wavelength specific coating for mirrored optics and method for reducing reflection of white light

Abstract

An amorphous diamond coating applied onto mirrored optics in an infrared motion sensor to block specific wavelengths of energy from a “white light” source like a halogen lamp, without reducing the reflectivity of the mirror surface in the Mid-Infrared wavelengths. A specific thickness of diamond-like-coating is applied on top of the reflective metal surface of a mirrored part, thereby reducing the mirror's reflectivity at visible and near-Infrared wavelengths known to be problematic for IR motion sensors, such as those emitted from halogen lamps. The coating has no significant detrimental effect on mid-Infrared reflectivity, so the IR motion sensor's performance is otherwise unaffected.

What is claimed is:  
     
       1. A method of reducing the incidence of visible and near-infrared light impinging on a reflective surface of an optical reflector in a motion sensor, comprising: 
       overlaying said reflective surface with a layer of non-crystalline carbon material;  
       said layer of non-crystalline carbon material having a thickness ranging from approximately 600 angstroms to approximately 1000 angstroms;  
       wherein said layer of non-crystalline carbon material absorbs visible and near-infrared light;  
       wherein said reflective surface reflects mid-infrared light passing through said layer of non-crystalline carbon material for detection by an infrared detector; and  
       wherein said layer of non-crystalline carbon material has an absorption spectra which is adjustable by adjusting said thickness.  
     
     
       2. A method as recited in  claim 1 , wherein said non-crystalline carbon material comprises amorphous diamond. 
     
     
       3. A method as recited in  claim 1 , wherein said non-crystalline carbon material comprises a diamond-like coating. 
     
     
       4. A method of reducing the incidence of visible and near-infrared light impinging on a reflective surface of an optical reflector, comprising: 
       coating said reflective surface with a diamond-like coating having a thickness ranging from approximately 600 angstroms to approximately 1000 angstroms;  
       wherein said diamond-like coating absorbs visible and near-infrared light;  
       wherein said reflective surface reflects mid-infrared light passing through said diamond-like coating for detection by an infrared detector;  
       and wherein said diamond-like coating has an absorption spectra which is adjustable by adjusting said thickness.  
     
     
       5. A method as recited in  claim 4 , wherein said diamond-like coating comprises a non-crystalline carbon material. 
     
     
       6. A method as recited in  claim 4 , wherein said diamond-like coating comprises an amorphous diamond material. 
     
     
       7. A mirror for a motion sensor having an infrared detector, comprising: 
       (a) a substrate base;  
       (b) a layer of reflective material adjacent to said substrate base; and  
       (c) a light absorbing layer adjacent to said layer of reflective material;  
       (d) said light absorbing layer having a thickness ranging from approximately 600 angstroms to approximately 1000 angstroms;  
       (e) wherein said light absorbing layer absorbs visible and near-infrared light;  
       (f) wherein said layer of reflective material reflects mid-infrared light passing through said light absorbing layer for detection by said infrared detector; and  
       (g) wherein said light absorbing layer has an absorption spectra which is adjustable by adjusting said thickness.  
     
     
       8. A mirror as recited in  claim 7 , wherein said light absorbing layer comprises a non-crystalline carbon material. 
     
     
       9. A mirror as recited in  claim 7 , wherein said light absorbing layer comprises an amorphous diamond material. 
     
     
       10. A mirror as recited in  claim 7 , wherein said light absorbing layer comprises a diamond like coating. 
     
     
       11. A mirror for a motion sensor having an infrared detector, comprising: 
       (a) a substrate base;  
       (b) a layer of reflective material adjacent to said substrate base; and  
       (c) a diamond-like coating over said layer of reflective material;  
       (d) said layer of reflective material comprising chrome;  
       (e) said diamond-like coating having a thickness ranging from approximately 600 angstroms to approximately 1000 angstroms;  
       (f) wherein said layer of reflective material mid-infrared light passing through said diamond-like coating for detection by said infrared detector; and  
       (g) wherein said diamond-like coating has an absorption spectra which is adjustable by adjusting said thickness.  
     
     
       12. A mirror as recited in  claim 11 , wherein said diamond-like coating comprises a non-crystalline carbon material. 
     
     
       13. A mirror as recited in  claim 11 , wherein said diamond-like coating comprises an amorphous diamond material. 
     
     
       14. A mirror for a motion sensor having an infrared detector, comprising: 
       (a) a substrate base;  
       (b) a layer of reflective material adjacent to said substrate base; and  
       (c) a layer of non-crystalline carbon material adjacent to said layer of reflective material, wherein said layer of reflective material is between said substrate base and said layer of non-crystalline carbon material;  
       (d) said layer of reflective material comprising chrome having a thickness of approximately 1700 angstroms;  
       (e) said layer of non-crystalline carbon material having a thickness ranging from approximately 500 angstroms to approximately 1000 angstroms;  
       (e) wherein said layer of non-crystalline carbon material absorbs visible and near-infrared light;  
       (f) wherein said layer of reflective material reflects mid-infrared light passing through said layer of non-crystalline carbon material for detection by said infrared detector; and  
       (g) wherein said layer of non-crystalline carbon material has an absorption spectra which is adjustable by adjusting said thickness.  
     
     
       15. A mirror as recited in  claim 14 , wherein said non-crystalline carbon material comprises a diamond-like coating. 
     
     
       16. A mirror as recited in  claim 15 , wherein said non-crystalline carbon material comprises an amorphous diamond material.